This invention relates to a contact pressure adjusting device in a heating and pressing fixing apparatus for electrophotographic copiers.
In the past, a heating and pressing fixing apparatus of the kind contemplated has been designed so that a heating roll and a press roll are rotatably brought into pressure contact with each other, and a copy paper is fixed as the paper passes between the heating roll and the press roll by the toner images carried by the paper contacting the heating roll.
There are many devices, in which contact pressure between the heating roll and the press roll is constant, while some devices are designed so that the stroke produced by a cylinder or solenoid may manually be varied to vary and adjust the contact pressure.
In either case, however, the contact pressure cannot be adjusted in a simple procedure, and hence, an adequate value of the contact pressure in accordance with variation in kind of paper quality cannot be achieved, resulting in inconveniences such as the lowering of copy quality and occurrence of paper wrinkle.
The present invention has been realized in view of circumstances noted above, and it is an object of the invention to provide a contact pressure adjusting decice in a heating and pressing fixing apparatus for electrophotographic copiers, which can adjust contact pressure automatically in a simple manner such as by pushing a button selector.